Photosensitive resin composition and pattern formation using the same

ABSTRACT

A photosensitive resin composition comprising (A) an alkaline aqueous solution-soluble novolak resin, (B) a photosensitizer obtained by reacting a polyhydroxy compound with 1,2-naphthoquinone-(2)-diazido-5(or 4)-sulfonyl chloride, and (C) an ultraviolet absorber such as 2-(2&#39;-hydroxy-5&#39;-methylphenyl)-benzotriazole, has a strong absorption against a light of a wavelength of 365 nm and is suitable for producing semiconductor elements, etc.

BACKGROUND OF THE INVENTION

This invention relates to a positive-type photosensitive resincomposition having strong UV light absorption and a process for forminga pattern using the same.

As fine processing technique for semiconductor elements, there is widelyemployed pattern formation using a positive-type photosensitive resincomposition and a g-line (light of 436 nm) projection aligner. In orderto improve the resolving power of a photosensitive resin, there areemployed an improvement of the photosensitive resin and an improvementof a light exposing device. The light exposing device can be improved byincreasing the numerical aperture of lens or making the exposingwavelength shorter. The resolving power is proportional to the exposingwavelength and can be improved by about 16% by changing the g-line toi-line (light of 365 nm). A light exposing device using a shorterwavelength of near 250 nm is now under development, but it requires amuch more time to accomplish such a device.

Thus, a light exposing device using i-line is noticed. As aphotosensitive resin used in such a device, there is used a compositioncomprising a novolak resin and 1,2-naphthoquinone-(2)-diazido-sulfonicacid ester as a photosensitizer (e.g. Japanese Patent ExaminedPublication Nos. 37-18015 and 54-20330, and Japanese Patent UnexaminedPublication Nos. 62-28457 and 62-89040). Such a photosensitive resincomposition can be used on a silicon oxide film and silicon nitridefilm, it but causes a problem of narrowing of patterns due to reflectedlight when used on a substrate having a high light reflectance such asan aluminum film.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photosensitiveresin composition of positive type having a small light reflectance froma substrate when the i-line is used, and strong light absorption.

The present invention provides a photosensitive resin compositioncomprising

(A) an alkaline aqueous solution-soluble novalak resin,

(B) a photosensitizer obtained by reacting at least one polyhydroxycompound selected from the group consisting of gallic acid esters,trihydroxybenzophenone and tetrahydroxybenzophenone, with1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride or1,2-naphthoquinone-(2)-diazido-4-sulfonyl chloride, and

(C) an ultraviolet absorber represented by the formula: ##STR1## whereinR₁ and R₂ are independently a hydrogen atom or an alkyl group having 1to 10 carbon atoms; and R₃ is a hydrogen atom or a halogen atom,

the amount of (A) being 90 to 71 parts by weight and the amount of (B)being 10 to 29 parts by weight, a total of (A) and (B) being 100 partsby weight, and the amount of (C) being 0.1 to 10 parts by weight basedon 100 parts by weight of the total of (A) and (B).

This invention also provides a process for forming a pattern, whichcomprises

coating the above-mentioned photosensitive resin composition on asubstrate,

drying the composition to form a photosensitive film, and

subjecting the photosensitive film to exposure to light and development.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The component (A) is an alkaline aqueous solution-soluble novolak resin.The words "alkaline aqueous solution-soluble" mean a resin soluble in analkaline aqueous solution such as an aqueous solution of 5% by weight orless of sodium hydroxide, potassium hydroxide, tetramethyl ammoniumhydroxide, chloline, or the like.

As the novolak resin, there can be used condensation resins of a phenolsuch as phenol, cresol, xylenol, or the like with formaldehyde, having asoftening point of preferably 135° to 165° C. from the viewpoint of heatresistance and synthesis. The softening point of novolak resin can beadjusted by a conventional method. The softening point can be obtainedaccording to JIS K 2207.

Such a novolak resin can be synthesized, for example, by reacting aphenol with formaldehyde in the presence of a catalyst such ashydrochloric acid, oxalic acid, or the like at 60° to 120° C. forseveral hours, and removing water and the unreacted phenol with heatingunder reduced pressure.

The photosensitizer (B) can be obtained by dissolving at least onepolyhydroxy compound selected from the group consisting of gallic acidesters such as methyl gallate, ethyl gallate, propyl gallate, etc.,trihydroxybenzophenone and tetrahydroxybenzophenone, and1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride or1,2-naphthoquinone-(2)-diazido-4-sulfonyl chloride in a solvent such asdioxane, tetrahydrofuran, acetone, methyl ethyl ketone, water,Cellosolve, etc. and reacting using a basic catalyst for acceleratingthe reaction.

As the basic catalyst, there can be used inorganic bases such as sodiumcarbonate, potassium carbonate, sodium hydroxide, potassium hydroxide,etc., and organic bases such as triethylamine, triethanolamine,diethylamine, etc.

The reaction temperature is not particularly limited, but is preferablyin the range of 0° to 40° C. from the viewpoint of the stability of themain product and reaction rate. Further, the reaction can preferably becarried out under a yellow light or a red light.

1,2-Naphthoquinone-(2)-diazido-5-sulfonyl chloride or1,2-naphthoquinone-(2)-diazido-4-sulfonyl chloride can be used in anamount of preferably 1.5 to 4 moles per mole of the polyhydroxycompound.

As the ultraviolet (UV) absorber (C), there is used a compound of theformula: ##STR2## wherein R₁ and R₂ are independently a hydrogen atom oran alkyl group having 1 to 10 carbon atoms; and R₃ is a hydrogen atom ora halogen atom.

Examples of the compound of the formula (I) are2-(2'-hydroxy-5'-methylphenyl)-benzotriazole,2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole,2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole,2-(2'-hydroxy-3',5'-di-t-amylphenyl)-benzotriazole,2-(2'-hydroxy-3',5'-di-t-butylphenyl)-benzotriazole,2-(2'-hydroxy-5'-t-butylphenyl)-benzotriazole,2-(2'-hydroxy-5'-t-octylphenyl)-benzotriazole, etc. These compounds canbe commercially available from Ciba-Geigy AG or Shipuro Kasei K.K., etc.

The alkaline aqueous solution-soluble novolak resin (A), thephotosensitizer (B) and the UV absorber (C) can be used in amounts of(A)/(B)=90 to 71/10 to 29 (weight ratio), a total of (A) and (B) being100 parts by weight, and 0.1 to 10 parts by weight of (C) per 100 partsby weight of the total of (A) and (B). When the amount of the alkalineaqueous solution-soluble novolak resin is more than 90 parts by weightand the photosensitizer (B) is less than 10 parts by weight, the totalof (A) and (B) being 100 parts by weight, a film loss at the time ofdevelopment increases. On the other hand, when (A) is less than 71 partsby weight and (B) is more than 29 parts by weight, the total of (A) and(B) being 100 parts by weight, sensitivity is lowered. When the amountof (C) is less than 0.1 part, the effect of absorbing UV rays is small,while when the amount of (C) is more than 10 parts by weight, thesolubility in a solvent becomes insufficient.

The photosensitive resin composition of the present invention mayfurther contain a solvent.

The positive-type photosensitive resin composition is dissolved in asolvent and coated on a surface of substrate made of, for example,silicon, aluminum, quartz, glass, etc.

As the solvent, there can be used ketones such as methyl ethyl ketone,methyl isobutyl ketone, cyclohexanone, etc.; aromatic solvents such astoluene, xylene, etc.; ethylene glycol monoalkyl ethers and alkoxy ethylacetates such as ethylene glycol monomethyl ether, mothoxyethyl acetate,ethoxyethyl acetate, etc.; esters such as ethyl acetate, butyl acetate,isoamyl acetate, etc.; alcohols such as methanol, ethanol, propanol,etc. These solvents can be used alone or as a mixture thereof.

In the photosensitive resin composition of the present invention, thephotosensitizer (B) is decomposed photochemically and becomes alkalineaqueous solution-soluble after the decomposition. The photochemicaldecomposition can be carried out by a conventional means such asirradiation with a mercury lamp, etc. As the alkaline aqueous solution,there can be used aqueous solutions of 5% by weight or less of sodiumhydroxide, potassium hydroxide, tetramethyl ammonium hydroxide, choline,and the like.

The photosensitive resin composition of the present invention mayfurther contain one or more conventionally used additives such asthermal polymerization inhibitors for improving storage stability,adhesiveness improving agents for improving adhesiveness to thesubstrate, etc., depending on purposes.

According to the present invention, a pattern can be formed on asubstrate made of, for example, silicon, aluminum, quartz, glass, etc.,by a conventional process, e.g. by coating the above-mentionedphotosensitive resin composition on the substrate, drying thecomposition to form a photosensitive film, and subjecting thephotosensitive film to exposure to light and development.

The present invention is illustrated by way of Examples, in which allparts and percents are by weight, unless otherwise specified.

EXAMPLE 1

A photosensitive resin composition was prepared by dissolving 20 partsof cresol novolak resin containing m-cresol/p-cresol in a weight ratioof 55/45 and having a softening point of 150° C. (hereinafter referredto as "(A-1)"), 6 parts of a photosensitizer obtained by reacting 1 moleof methyl gallate with 2.5 moles of1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride (hereinafter referredto as "(B-1)") and 0.52 part of2-(2'-hydroxy-5'-methylphenyl)-benzotriazole (mfd. by Shipuro KaseiK.K.) in 74 parts of ethoxyethyl acetate.

The resulting composition was spin coated on a silica substrate at 3000rpm for 30 seconds, and dried at 90° C. for 20 minutes to give alight-sensitive film of 1 μm thick.

The resulting substrate was subjected to measurement of transmittanceusing a spectrophotometer (mfd. by Hitachi, Ltd.) at a wavelength of 365nm with a result of as low as 18%. Thus, a strong absorption wasobtained.

The above-mention composition was coated on a silicon wafer having analuminum film thereon under the same conditions as mentioned above, andexposed to a light of 365 nm using a light exposing device LD-5010 i (atrade name, mfd. by Hitachi, Ltd.) via a photo-mask for 700 msec.,developed by using an aqueous solution 2.38% of tetramethyl ammonium(hereinafter referred to as "Developing solution (1)") at 23° C. for 60seconds, and rinsed with deionized water for 60 seconds to give apattern having a line width of 0.7 μm.

EXAMPLE 2

A photosensitive resin composition was prepared by dissolving 20 partsof cresol novolak resin containing m-cresol/p-cresol in a weight ratioof 60/40 and having a softening point of 155° C. (hereinafter referredto as "(A-2)"), 5.5 parts of a photosensitizer obtained by reacting 1mole of 2,3,4-trihydroxybenzophenone with 3 moles of1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride (hereinafter referredto as "(B-2)") and 0.77 part of2-(2'-hydroxy-5'-t-butylphenyl)-benzotriazole in 74 parts of ethoxyethylacetate.

A light-sensitive film of 1 μm thick was obtained in the same manner asdescribed in Example 1 using the above-mentioned composition.

The resulting substrated was subjected to the measurement oftransmittance at a wavelength of 365 nm in the same manner as describedin Example 1. The obtained value was as low as 17%. Thus, a strongabsorption was obtained.

EXAMPLE 3

A photosensitive resin composition was prepared by dissolving 20 partsof (A-1) as a cresol novolak resin obtained in Example 1, 5.5 parts of aphotosensitizer obtained by reacting 1 mole of2,3,4,4'-tetrahydroxybenzophenone with 3.3 moles of1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride (hereinafter referredto as "(B-3)") and 1.0 part of2-(2'-hydroxy-5'-t-octylphenyl)-benzotriazole in 75 parts of ethoxyethylacetate.

Using said composition, a light-sensitive film of 1 μm thick wasobtained in the same manner as described in Example 1.

The resulting substrate was subjected to the measurement oftransmittance at a wavelength of 365 nm in the same manner as describedin Example 1. The obtained value was as low as 12%. Thus, a strongabsorption was obtained.

COMPARATIVE EXAMPLE 1

A photosensitive resin composition was prepared in the same manner asdescribed in Example 1 except for not using2-(2'-hydroxy-5'-methylphenyl)-benzotriazole. The photosensitive resincomposition was coated on a silica substrate to give a light-sensitivefilm of 1 μm thick. The transmittance at a wavelength of 365 nm measuredin the same manner as described in Example 1 was 25%.

COMPARATIVE EXAMPLE 2

A photosensitive resin composition was prepared in the same manner asdescribed in Example 2 except for not using2-(2'-hydroxy-5'-t-butylphenyl)-benzotriazole. A light-sensitive filmwas prepared in the same manner as described in Example 1 using theabove-mentioned composition. The transmittance of a wavelength of 365 nmmeasured in the same manner as described in Example 1 was 25%.

COMPARATIVE EXAMPLE 3

A photosensitive resin composition was prepared in the same manner asdescribed in Example 3 except for not using2-(2'-hydroxy-5'-t-octylphenyl)-benzotriazole. A light-sensitive filmwas prepared in the same manner as described in Example 1 using theabove-mentioned composition. The transmittance at a wavelength of 365 nmmeasured in the same manner as described in Example 1 was 24%.

As mentioned above, the photosensitive resin composition of the presentinvention has a strong absorption against the i-line light (wavelength365 nm), and an effect of lessening light reflection from a substrate.Thus, the photosensitive composition of the present invention can beapplied to various industrial fields such as photographic industry,printing industry, electronic industry, and the like.

What is claimed is:
 1. A photosensitive resin composition providing a film having a high absorbency for a wavelength of 365 nm comprising an admixture of(A) an alkaline aqueous solution-soluble novolak resin, (B) a photosensitizer that is a reaction product of methyl gallate and 1,2-naphthoquinone-(2)-diazido-5-sulfonyl chloride, and (C) an ultraviolet absorber represented by the formula: ##STR3## wherein R₁ and R₂ are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; and R₃ is a hydrogen atom or a halogen atom, the amount of (A) being 90 to 71 parts by weight and the amount of (B) being 10 to 29 parts by weight, a total of (A) and (B) being 100 parts by weight, and the amount of (C) being 0.1 to 10 parts by weight based on 100 parts by weight of the total of (A) and (B).
 2. A photosensitive resin composition providing a film having a high absorbency for a wavelength of 365 nm comprising an admixture of(A) an alkaline aqueous solution-soluble novolak resin, (B) a photosensitizer that is a reaction product of methyl gallate and 1,2-napthoquinone-(2)-diazido-5-sulfonyl chloride, and (C) an ultraviolet absorber that is 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)-benzotriazole, or 2-(2'-hydroxy-5'-tert-octylphenyl)-benzotriazole, the amount of (A) being 90 to 71 parts by weight and the amount of (B) being 10 to 29 parts by weight, a total of (A) and (B) being 100 parts by weight, and the amount of (C) being 0.1 to 10 parts by weight based on 100 parts by weight of the total of (A) and (B). 